textproduct: Albany

WHAT HAS CHANGED

There continues to be uncertainty in the timing of a cold front that will drive showers and thunderstorms on Sunday. Based on the latest trends, this front now looks to make its passage through the region in the late afternoon/early evening Sunday through Sunday night. This may reduce the severe weather potential to a shorter window late Sunday afternoon through Sunday evening when sufficient instability will still be in place. That said, while greater than normal uncertainty at this short a lead time errs to low confidence in the overall severe threat, high confidence exists in the occurrence of widespread showers with the potential for embedded, non-severe thunderstorms (25-40% probability of thunder Sunday into Sunday night).

The Storm Prediction Center has shifted the previously issued Slight Risk (Level 2 of 5) for severe thunderstorms on Sunday slightly farther south and west. Greater portions of the Southern Adirondacks, Upper-Hudson Valley, Southern Greens, and now a small portion of Berkshire and Litchfield Counties have therefore been reduced to a Marginal Risk (Level 1 of 5). Severe wording was therefore added to the forecast for areas within the Slight Risk area to message the potential for gusty winds. Additionally, given the potential for heavy downpours, we also added a mention of heavy rainfall for all areas into Sunday's weather forecast as well.

KEY MESSAGES

1) There is potential for isolated to scattered severe thunderstorms on Sunday, particularly for areas along and south of I-90, with the primary hazard of damaging wind gusts.

2) A reprieve from the well-above normal heat comes in time for the new work week as temperatures return to more seasonable levels. And while we start off on a dry note Monday and Tuesday, additional chances for showers and thunderstorms come for the middle to possibly the end of the week.

DISCUSSION

KEY MESSAGE 1...

High pressure nosing northward from the Ohio/Tennessee River Valleys will bring a nice break from showers and thunderstorms today, before probabilities for both increase once again tomorrow. And, courtesy of drying conditions both from the high and yesterday's cold front, we'll also get a break from the oppressive heat. Though highs will be in the mid 70s to upper 80s, it will certainly feel more comfortable given dew points in the 50s to low 60s. Tomorrow, a southerly flow regime will become established across the region, allowing temperatures and dewpoints to increase by a few degrees. Highs will reach the upper 70s to upper 80s with pockets near 90 in valley areas. Dewpoints maximizing in the upper 50s to mid 60s won't be sufficient to pose a risk for dangerous heat indices, but continue to drink plenty of fluids, apply sunscreen if spending time outdoors, and have a plan to take frequent breaks from the heat in a cooled location. These temperatures could still pose the risk of heat-related illness, particularly for those who are susceptible, if proper precautions are not taken.

While tomorrow will start out dry, the probability of showers and thunderstorms, some of which could become severe, increases beginning in the afternoon. A potent, deepening shortwave trough rotating through the base of a closed, upper low will dig through the Upper- Midwest tomorrow morning, entering the Ohio Valley/eastern Great Lakes and taking on a negative tilt by tomorrow afternoon. Meanwhile, a series of surface lows look to develop in the Midwest and eastern Great Lakes along a northeast to southwest oriented cold frontal boundary attending a primary low around the James Bay area. The combined forcing for ascent within the encroaching shortwave, surface lows, and cold front will be sufficient to drive potentially widespread showers and thunderstorms across the region late tomorrow afternoon and potentially through tomorrow night.

That said, there continues to be a great deal of uncertainty particularly pertaining to the timing of the incoming front and subsequently the window of opportunity for the aforementioned resulting thunderstorms to have the potential to become severe. The Storm Prediction Center has maintained a Slight Risk (Level 2 of 5) across much of our region for tomorrow, with the primary hazard of damaging wind gusts. However, with the latest ensembles and even some of the deterministic guidance indicating a delayed passage of the front until late tomorrow afternoon/early tomorrow evening through tomorrow night, there is a very real possibility that we won't have enough instability to trigger severe storms. That said, this could be a low CAPE/high shear situation (<1000 J/kg MLCAPE and 30-40kt 0-6 km shear) wherein just enough instability pairs with high values of shear to trigger some strong, organized updrafts that allow storms to reach severe strength. Given fast storm motion (0-6 km mean wind ~30kt), straight hodographs, high precipitation content, and steep pressure changes there certainly is potential for gusty winds within any thunderstorm that develops tomorrow. But whether storms can produce severe magnitude gusts is going to depend highly on the available energy to transfer that momentum to the surface. We will continue to monitor this threat closely over the coming hours.

KEY MESSAGE 2...

With the aforementioned frontal passage complete by early Monday morning, drying conditions in its wake will ensure a dry start to the work week with actually below normal temperatures. Highs Monday will largely be in the 60s and 70s before a slight increase brings us closer to normal on Tuesday. Highs then will be in the upper 60s to upper 70s with pockets near 80 in the lower Mid-Hudson valley. The remainder of the week will maintain comfortable and near to slightly above normal temperatures with chances for showers and thunderstorms increasing again beginning Wednesday afternoon.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

VFR conditions prevail through the end of the TAF period. West to northwesterly winds will strengthen by around 15 - 18 UTC becoming sustained 8 and 12 knots with gusts up to 15 knots.

Outlook...

Saturday Night: No Operational Impact. NO SIG WX. Sunday: High Operational Impact. Breezy. Likely SHRA...TSRA. Sunday Night: High Operational Impact. Breezy. Definite SHRA...TSRA. Monday: Low Operational Impact. Breezy. NO SIG WX. Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: Moderate Operational Impact. Chance of SHRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.